Optical fibers are glass strands capable of transmitting an optical signal over great distances, at very high speeds, and with relatively low signal loss relative to standard copper wire networks. Optical cables are therefore widely used in long distance communication and have replaced other technologies such as satellite communication, standard wire communication etc. Besides long distance communication, optical fibers are also used in many applications such as medicine, aviation, computer data servers, etc.
Due to the broad range of applications for optical fibers, optical cables may need to be capable of operation in harsh environments. For example, optical cables may be used in harsh environments where high chemical resistance is needed such as in ducts, refineries such as oils and gas plants, mining operations, and the like. Optical cables may also be relied upon to maintain functionality for safety reasons during disaster events. For instance, optical cables may need to be flame retardant, fire resistant, and maintain circuit integrity for as long as possible during a fire. In addition, the performance of optical cables may be adversely affected by pressure events such as bending, buckling, and compressive stresses. For these reasons, optical cables that are resistant to chemicals, fire, and/or mechanical stresses may be desirable.
Optical cables may also be used in applications where electrical signals and/or electrical power are desirable in addition to an optical signal. A hybrid cable may include electrically conductive pathways as well as optical pathways in an integrated cable solution. For example, optical devices and electronic equipment such as machinery, sensors, communication devices, and others may be fed by a hybrid cable. Hybrid cables have been described previously in the art.
A fiber-optic transmission cable for high-stress environments and especially undersea applications is described by Stamnitz in European Patent Publication No. EP0371660A1. The fiber-optic transmission cable comprises one to a large number of optical fibers, electrical conductors, and metallic wire strength members contained within a single cable structure. A specific example is an electro-opto-mechanical cable that includes at least one thin-wall steel alloy tube containing at least one single mode fiber and a void filling gel. A dielectric annulus includes an electrically conductive layer disposed therein. An optional double-layer contrahelical or three or four layer, torque balanced, steel wire strength member provides additional protection as well as capability to be towed, deployed and recovered from the seafloor at abysmal depths.
An undersea telecommunications cable is described by Marlier et al. in U.S. Pat. No. 5,125,061. The undersea telecommunications cable has optical fibers embedded in a material filling a tube which itself lies inside a helical lay of metal wires having high mechanical strength and in which the interstices are filled with a sealing material. The cable includes a first extruded sheath between the tube and the helical lay, and the helical lay is itself covered by a second extruded sheath which is insulating and abrasion resistant, and if the cable is for a remotely-powered link, it includes a conductive strip on the tube or on the first sheath.